Solar altitude detectors are used in motor vehicles for the purpose of controlling the temperature of the internal compartment of the vehicle. For example, DE 40 41 770 C1 discloses a solar sensor which in dependence upon the intensity of the solar radiation serves to control the air conditioning system in a motor vehicle. This type of solar sensor essentially consists of an optoelectronic transducer which has a lens connected upstream thereof for the purpose of detecting the broadest possible section of the environment. Although this type of device is able to detect the radiation intensity of incident sunlight, it is not possible to detect the solar altitude.
DE 38 21 743 A1 discloses a solar altitude detector, wherein two solar sensors of this type are provided as the sensor unit. The sensors are disposed with respect to each other in such a manner that it is possible to identify the direction of incidence of the light. For this purpose it is possible to dispose the two sensors in an angular manner with respect to each other or to separate them from each other by means of a shade mask or separating disc. The light intensities which are detected by the two sensors are different in dependence upon the incidence of light, so that this difference can be used to indicate the radiation direction. The two solar sensors are connected to a processor unit which evaluates the detected solar intensity and which can control the air conditioning system irrespective of the side of the vehicle.
This type of solar altitude detector is conventionally disposed on the upper side of the motor vehicle instrument panel behind the windscreen. The shade mask points in the direction of travel, so that a left-hand solar sensor and a right-hand solar sensor are formed. If sunlight impinges upon this solar altitude detector from the front or from above, this irradiates both the left-hand solar sensor and the right-hand solar sensor to the same extent. Consequently, the air conditioning installation which is allocated to each side of the vehicle is controlled in an identical manner. In contrast, if the sunlight impinges upon the solar altitude detector at a lateral angle, i.e. from the passenger side, then the right-hand solar sensor will detect the solar intensity. Conversely, the left-hand solar sensor is shaded by virtue of the disc-like shade mask. This different solar intensity detection in the two solar sensors directly indicates an approximate solar altitude, namely on the right-hand side, middle or left-hand side. It follows from this example that the air conditioning system on the passenger side exposed to sunlight is consequently controlled to provide a greater cooling effect than the air conditioning system on the driver side which is in the shade.
This known solar altitude detector renders it possible to detect the solar altitude on a right-hand side, middle, left-hand side basis. However, it is desirable to be able to detect the solar altitude with the aid of a solar altitude detector, wherein it is not only possible to detect the solar altitude with respect to the right-hand side, middle, left-hand side-arrangement, but it is also possible to detect the solar altitude within the half space located above a vehicle. This type of method of detecting the solar altitude is particularly desirable if further solar altitude-dependent functions, such as e.g. tinting control of electrochromic vehicle windows are required.
DE 195 48 578 A1 discloses a position-selective passive infra-red intrusion sensor. This sensor is used to detect moving and static heat being radiated by objects for the purpose of determining the position of said objects and for the purpose of determining the direction of movement of objects of this type. For the locating process, the sensor unit comprises a plurality of receivers which cover different angle ranges, wherein the angle ranges of adjacent receivers overlap in regions. The output signals of the receivers are then ascertained by virtue of a comparison of the intensities received in the different receivers, from which it is possible to determine the direction of incidence of the received heat radiation. However, this device is not suitable for use in detecting the solar altitude in relation to a motor vehicle.
A further solar altitude detector is known from AT 403 095 B. The subject matter of this document relates to a solar radiation measuring sensor for global and diffuse radiation. In the case of the solar altitude detector which is disclosed in this document a vertically disposed shade dispenser rod is provided, in whose base region a number of photosensitive receivers are disposed concentrically, surrounding said shade dispenser rod in an annular manner. In dependence upon the direction of incidence of the solar beams different receivers are shaded, from which it is possible to derive the direction of incidence of the solar beams. This device is also not suitable for detecting the angle of incidence--the azimuth. Furthermore, a disadvantage of this known solar altitude detector is that it is formed in a dome-shaped manner, which in turn prevents the solar altitude detector from being disposed on the motor vehicle body.